Light sensitive diazotype materials



of the diazo in the light struck areas.

United States Patent LIGHT SENSITIVE DIAZOTYPE MATERIALS Joseph F. Kosalek, Binghamton, and John Sulich, :In, Endicott, N. Y., assignors to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application February 10, 1954, Serial No. 409,523

12 Claims. (Cl. 96-91) The present invention pertains to light sensitive diazotypeimaterials having fast printing speed and being capable of yielding images of high density, and more particulafrly to such materials in which the light sensitive component is located on the base in a layer comprising a water soluble to Water dispersible polymeric material having finely divided alumina dispersed therethrough.

It has become customary with users of the diazotype process and sensitized materials therefor to demand faster printing materials which, at the same time, yield images of higher density upon a clean white background. Inasmuch as the diazotype process in commercial use is a bleach-out, positive process, it is manifest that problems are encountered in meeting these demands. If, for eX- ample, one uses a given diazo of a certain ultraviolet light sensitivity, it is obvious that a reduction in concentration of the diazo will permit one to achieve faster printing speed. This is, of course, attributable to the fact that one need burn out less diazo in order to obtain the image. It is equally evident, however, that the increase in printing speed is only obtained by a sacrifice in the azo dye density of the image produced by development. Meeting the requirements of the art is, therefore, not as simple as V it appears.

The difi'iculties involved have been recognized and have been grappled with by those in the industry. Several shrewd approaches to a solution have been made, certain of which have achieved great success and others of which have been of little moment. Despite the progress which has been made, the art is a long way from providing a product of optimum characteristics.

The most obvious approach to the problem involved is the selection of a diazonium compound having such a high light sensitivity that it may be used in a concentration which will give the required image density while still permitting complete burn-out in the whites in the desired period of time. To this end, numerous diazos of widely varied chemical structures have been proposed, synthesized and tested in the diazotype process. Of these compounds, the stabilized diazos derived from N,N-disubstituted p-phenylenediamines appear to offer the best compromise between high light sensitivity and greater dye density, on the one hand, and the other requisite features such as water solubility in coating solutions, stability to decomposition and/ or precoupling, fastness properties and the like, on the other hand.

Another tack has been the use of additives in the diazotype coating solution to increase the burn-out sensitivity For this purpose, there have been proposed such compounds as anthraquinone disulfonic acid, ketonic organic compounds and the like. It is evident that this phenomenon, if successful, would permit more diazo to be used in the sensitized layer and thereby result in a higher density in the image areas with no sacrifice in printing speed. Unfortunately, this approach has met with but limited success, the results not being commercially satisfactory on a quality or cost basis.

A further approach has been to utilize the image sur- Patented Dec. 4, 1956 face more efficiently by the application of a more or less discontinuous layer of a chemically-inert, but physicallyactive, finely divided material such as finely divided silica. In this procedure, it has been suggested that such layer be applied by pretreatment of the base or that it be layed down from the coating solution. Thus, U. S. P. 2,433,- 515 (Reissue 23,510) suggests the formation of a dis crete siliceous layer from a colloidal liquid dispersion of silica as a pretreatment for paper, which is then sensitized with a blue print solution. It is claimed that the brightness and density in the resulting printare thereby enhanced. Conversely, U. S. P. 2,566,709 proposes to produce the same improvement in the diazotype system of photo reproduction by the incorporation of colloidal silica in a dispersed state in a diazotype sensitizing solution. The latter procedure has the very important added economic advantage of eliminating a separate coating step.

It has been found in practice, however, that these two procedures possess certain disadvantages, the gravest of which are (l) rub-oft; (2) the action of the silica layer as a chromatographic separator, and (3) cost.

Rub-off, or powdering-off, as the name implies, involves the tendency of the silica particles to be removed during manufacture and end use of the diazotype materials. This action is not only very annoying but in addition may present potential health hazards.

. It has been ascertained also that the silica layer acts as a chromatographic separator toward the several ingredients present in a typical diazo coating solution. This results in poorer stability, poorer fade resistance, and in the case of the black line (which uses a multiplicity of coupling components) off-colored blacks.

It has been stated that the use of the silica layers in the above patents enhanced brightness and density. It i to be noted, however, that the degree of improvement when weighed against the aforesaid objections, the increased cost and extra efforts is disappointingly small. 7

In U. S. P. 2,662,013 issued December 8, 1953, it is suggested that the above disadvantages be eliminated by the use of binding agents for the silica particles. As such binding agents it is proposed to use those containing chemically bound nitrogen, either in the form of naturallyoccurring proteinaceous materials or synthetic resins. It was discovered that the proper ratio, experimentally determined, of silica to binder was of critical importance. In fact, it was found that at the proper ratio of silica and binder, a synergistic effect took place, to Wit, density enhancement was out of all proportion to that obtained when either component was used alone or when the two were used together at concentrations other than optimum. Further studies revealed that silica particles of 1 to 5 micron size gave appreciably greater density enhancement than the smaller particles recommended in the aforesaid patents. However, particles above 10 micron size were avoided since they were difiicult to maintain in suspension in the precoating bath and produced undesirable surface roughness in the dried coating.

The procedure of the above patent was a marked commercial advance. However, it had one drawback, this being the incompatibility of the suggested binders with the requisite ingredients of the sensitizing solution. As a consequence, it is necessary in operating according to the above patent to apply the silica-binder dispersion in a separate precoating operation. The use of two coating operations, coupled with the extra handling of the materials involved, manifestly increases the production costs.

We finally discovered that the advantages of the above procedure would be obtained while avoiding the addition of the coating step by utilizing alumina rather than silica as the pigment and, as the binder for the alumina, a water soluble to water dispersible polymeric material 7 form tme colloidal solutions in water.

compatible with the ingredients of the sensitizing solution. Sensitizing solutions containing said polymeric material as the binder along with finely divided alumina, light sensitive diazotype materials prepared from such compositions and the processing of such diazotype materials constitute the purposes and objects of the present invention.

The polymeric material, the use of which is contemplated. herein, may be a natural p'roductsuch as gelatin or a starch, i. e., corn starch, wheat starch, potato starch or the like, or it may be a synthetic product such as methyl cellulose, polyvinyl alcohol, sodium cellulose sulfate, polymethacrylic acid, polyarcrylic acid, hydroxyethyl cellulose, urea formaldehyde resins, melamine formaldehyde resins, methylated starch, chlorinated starch, carboxylated starch or the like. All of these materials are well known in the industry and the preparation of the synthetic products has been described in the literature.

With the exception of the starches, the listed products are water soluble. This means, of course, thatthe urea formaldehyde and melamine formaldehyde resins are of a low stage of condensation. Dissolution of the melamine formaldehyde oondensation product may be facilitated according to customary practice by acidifying with a small amount of a weak acid such as citric acid.

The starches, as is known, are water dispersible and Such colloidal solutions, like the water solutions of the other binders previously mentioned, are compatible with the components of the sensitizing solutions and do not cause premature precipitation thereof.

The water solutions or dispersions of the polymeric materials contain the polymeric material in a quantity of about 45 to 55% by weight.

The alumina which we use in our dispersions may be either colloidal in character or may be of a coarser grade, i. e., ranging from 1 to 5 microns in size. We find that we obtain best results with the coarser particles and so prefer their use.

Any of the usual light sensitive diazonium compounds may be employed and, in this connection, reference is made to the-compounds referred to in U. S. P. 2,501,874 and in the article by Van der Grinten, Photographic Journal, vol. 92B, 1952, page 46. The stabilized diazos derived from N,N-di-substituted p-phenylene-diamines are most satisfactory. Examples of such diazos are those derived from N,N-diethyl-p-phenylenediamine; N-benzyl- N ethyl p phenylenediamine; N ethyl p phenylenediarnine; N phenyl p phenylenediamine; N,N- diethyl 2' ethoxy p phenylenediarnine; N ethyl-2- methyl p phenylenediamine; N,N bis(,8 hydroxyethyl) p phenylenediamine; N B hydroxyethyl-N- methyl-p-phenylenediamine and the like. According to customary procedure, these diazos are used in the form of salts stabilized with zinc chloride, tin chloride, cadmium chloride and the like.

The comments with regard to the diazonium compounds apply equally to the coupling components. Thus, any of the usual coupling components are satisfactory for our purpose. Examples of such couplers are 2,5- Xylenol; 2,3-dihydroxynaphthalene; 1,8-dihydroxynaphthalene; resorcinol, octyl resorcinol; p-methyl-N-phenyl pyrazolone; the amide of aesorcylic acid; 2-hydroxynaphthalene-3,6-disulfonic acid; H acid; acetyl acetanilide; 2,341ih-ydroxynaphthalene-6-sultonic acid and the like. Other couplers are mentioned in the Van der Grinten article supra. I

The coating solution, in addition to the polymeric material, alumina and light sensitive diazo may contain the various adiuncts usual in the manufacture of light sensitive diazotype materials. These include metal salts for intensification of the dyestuff image, such as ammonium sulfate, nickel sulfate, zinc chloride and the like; stabilizing agents such as thiourea, thiosinamine, naphthalene trisulfonic acid and the like; acids acting to retard precoupling such as acetic acid, boric acid, tartaric acid and the like; hygroscopic agents such as glycol, glycerin and the like; and wetting agents such as saponin, lauryl sulfonate, keryl benzene sulfonate, the oleic acid amide of N-methyl taurine and the like.

It is also recommended that agents be used which have the property of accelerating the rate of azo dye color development, particularly under conditions of low ammonia concentration. For this purpose, there are used thiourea derivatives and particularly those in which either one or both nitrogen atoms are substituted by an aliphatic radical. Examples of such compounds are 1-alIyl-3-,6-hydroxyethyl-Z-thiourea; 1-allyl-2-thiourea and the like.

The ratio of alumina to binder is not as critical in our procedure as in the procedure of U. S. P. 2,662,013. Thus, the quantity of binder may range from A5 to 1 part by weight for each part by weight of alumina. The quantity of alumina, on the other hand, based on the Weight of the light sensitive diazonium compound is about 1 part of the diazonium compound to 1 to 4 parts of alumina.

The base to which our coating solution is applied may be any of the bases which have been previously suggested for use in the diazotype field. Examples of such bases are high grade all-sulfite bond paper, rayon or cotton cloth, starch filled cloth, partially hydrolyzed cellulose acetate filmbase, regenerated cellulose acetate and the like.

One of the particular advantages of our development is the fact that it may be used not only with the dry development process, but also with the one component moist process. It is recommended that when the latter procedure is employed, a small amount of a fluoride be added to improve the solubility of the diazo in the coating solution. For this purpose, there may be employed ammonium bifiuoride, sodium fluoride, potassium fluoride and the like. Generally, these salt-s are added in an amount ranging from .5 to 4 grams per hundred cc. of coating solution.

Our procedure is carried into effect by dissolving in water, the various components of the sensitizing solution and then dispersing therein the desired quantity of alumina and polymeric material. Any of the apparatus usual for the formation of dispersions may be employed. The base is then coated with the suspension, dried and processed either by the dry or wet method, depending upon whether the coating solution is a two or one component solution.

The invention will be more fully understood from the following examples which are illustrative only. The parts are by weight unless otherwise stated.

Example I High grade all-sulfite bond paper is coated with a sensitizing solution of the following composition:

Water to cc.

and dried. Prints made from these coatings show a considerable enhancement in density when compared to prints made on paper similarly treated with coating solution containing no alumina binder. When compared to prints from coatings made from a solution containing all the above ingredients except the polyvinyl alcohol, the former Inf had appreciably greater dye density and brightness and showed no tendency for the alumina pigment to rub off, while the latter were markedly inferior in all three respects.

Example II High grade all-sulfite bond paper is coated with a sensitizing solution of the following composition:

Water cc 60 Ethylene glycol or glycerol cc 5 Isopropanol cc 1 Citric acid gms Zinc chloride gms.. 5 N-fl-hydroxyethyl-N'-allyl thiourea gms 2.5 Diresorcyl sulfoxide gms 1.3 Acetoaeetanilide gm 0.07

, 2,3-dihydroxy naphthalene-6-sulfonic acid gms 1.9

4-N,N-diethylamino benzene diazonium chloride zinc chloride double salt gms 3 Finely divided alumina of 1-5 micron size gms 6 50% solids corn starch aqueous dispersion cc 3 Sapom'n "gm..- 0.01

Water to 100 cc.

and then dried. Prints and comparisons made in a fashion analogous to those in Example I reveal the same improvements.

Example III A high grade, well-sized bond paper is coated with Water to 100 cc.

and then dried. Prints were made and developed in an aqueous solution composed of:

Water c 100 Sodium carbonate gms 2 Sodium thiosulfate gms 5 Thiourea gms 2.5 Tertiary sodium phosphate gm 0.5 Sodium chloride gms 4 Phloroglucinol gm 1 Resorcinol gm 0.5

When these were compared to similarly .made prints whose coatings were from a solution not containing the proposed additives, the former were considerably superior in density;

Example IV The procedure is the same as in Example I excepting that the polyvinyl alcohol is replaced by 3 cc. of a 50% solution of methyl cellulose.

Example V The procedure is the same as in Example II excepting that the starch is replaced by 3 cc. of a 50% solution of a urea formaldehyde condensation product.

Various modifications of the invention will occur to persons skilled in the art. Thus, it is evident that in lieu of the polymeric materials recited in the examples, any polymeric material mentioned above may be utilized. We, therefore, do not intend to be limited in the patent granted except as necessitated by the appended claims;

We claim: I

1. A light sensitive composition for diazotype materials comprising a compatible aqueous dispersion of a light sensitive diazonium compound, coupling component, a polymeric binder material selected from the classconsisting of water soluble to water dispersible starches and water soluble polyvinyl compounds and'finely divided alumina.

2. The composition as defined in claim 1 in which the polymeric material is a water soluble synthetic polyvinyl resin.

3. The composition as defined in claim 1 wherein the polymeric material is a starch.

4. The composition as defined in claim 1 wherein the polymeric material is a polyvinyl alcohol.

5. The composition as defined in claim 1 wherein the polymeric material is polyacrylic acid.

6. The composition as defined in claim 1 wherein the alumina has a particle size ranging from 1 to 5 microns.

7. A water receptive base impregnated with a light sensitive composition comprising a compatible aqueous dispersion of a light sensitive diazonium compound, coupling component, a polymeric binder material selected from the class consisting of water soluble to water dispersible starches and water soluble polyvinyl compounds and finely divided alumina.

8. The article as defined in claim 7 wherein the polymeric material is a water soluble synthetic polyvinyl resin.

9. The article as defined in claim 7 wherein the polymeric material is a starch. a

10. The article as defined in claim 7 wherein the polymeric material is polyvinyl alcohol.

11. The article as defined in claim 7 wherein the polymeric material is polyacrylic acid.

12. The article as defined in claim 7 wherein .the'

alumina has a particle size ranging from 1 to 5 microns.

References Cited'in the file of this patent UNITED STATES PATENTS 2,205,991 Neugebauer June 25, 1940 2,239,704 DeBoer et al Apr. 29, 1941 2,545,057 Von Glahn et al Mar. 13, 1951 2,616,803 Ravich Nov. 4, 1952 FOREIGN PATENTS 702,294 Great Britain Jan. 13, 1954 

1. A LIGHT SENSITIVE COMPOSITION FOR DIAZOTYPE MATERIALS COMPRISING A COMPATIBLE AQUEOUS DISPERSION OF A LIGHT SENSITIVE DIAZONIUM COMPOUND, COUPLING COMPONENT, A POLYMERIC BINDER MATERIAL SELECTED FROM THE CLASS CONSISTING OF WATER SOLUBLE TO WATER DISPERSIBLE STARCHES AND WATER SOLUBLE POLYVINYL COMPOUNDS AND FINELY DIVIDED ALUMINA. 